1. Field of the Invention
This invention relates to methods and apparatus for transporting ocean bound migratory fish from spawning streams to the brackish waters of a tidal basin.
2. Description of the Prior Art
Salmon and steelhead depend on great rivers like the Snake and Columbia for their passage ways to and from the ocean. The wonderful Northwestern country, with its maze of rivers and tributaries stretch across three states and extend into two more. These streams and hundreds of smaller tributaries are both the beginning and the final life cycle for these anadromous fish. Although they spend only two years of their life in the ocean, this cycle is critical to their survival as a species. Salmon and steelhead flourished hundreds of years before man built obstructions across these rivers. These dams however, gave us new living standards by furnishing hydro-electrical power and water for our crops. Although these dams are obviously a very desirable resource, their presence limits the passage of the species to complete their 5.5 year life cycle. The lack of an adequate system to allow this passage has greatly reduced and endangered one of our greatest natural resources.
There is currently, and has been for some time, a critical need to provide a method and apparatus which will successfully transport young migratory fish, also known as fry, fingerlings, and smolt, from their spawning grounds, over, often a series of dams, and to the ocean.
Presently, fish are simply released and are expected to find their way, through fish ladders, to the ocean. Very few make it. The overwhelming mass of fish being destroyed by the hydroelectric turbines of the dam. Those that aren't, become easy prey for predators, both fish and bird, as they linger in and become accustomed to the brackish waters, before entering the sea.
Efforts to solve this problem have resulted in several conduit systems for transporting fish, best typified by the excellent efforts of D. L. Koch, U.S. Pat. No. 4,437,431 and R. J. Zimmerman, U.S. Pat. No. 4,629,361.
Koch described and claims a system including conduits for receiving fish, located with the reservoir of a dam; the creation of an artificial stream within the conduits; and an extension of the conduit over or around the dam, terminating into the tailrace area downstream of the dam.
Zimmerman describes a system, devoid of mechanical devices, which extends past dams or other obstructions below and parallel with the surface of the stream. While ideal in many respects, Zimmerman's system is impractical for existing dams with hydroelectric capabilities because of cost of building a system that would be stream level through or around the dam.
Both Zimmerman and Koch recognize the problem of enticing fish to enter a dark passageway and both suggest the use of transparent conduits to solve this problem. This solution, however, is seriously flawed in that the fish will return to the intake of the conduit upon coming to areas of darkness. When the stream or reservoir waters are murky; where the conduit is located too far below the water surface; and where silt, algae, and debris cling to the top surface of the conduit, insufficient light enters the pipe and fish refuse further downstream movement.